Embodiments of the present invention generally relate to methods, devices, and systems for reducing a pigmentation of a skin of a patient. More specifically, embodiments generally relate to methods, devices, and systems to increase the chance of freezing (water phase transition) in the skin.
Controlled freezing of biological tissue, such as skin tissue, can produce various effects. Certain tissue freezing procedures and devices, such as conventional cryoprobes, can cause severe freezing of tissue and generate cellular damage. It has been observed that moderate degrees of freezing can produce particular effects, such as affecting the expression of skin pigmentation.
There is a demand for cosmetic products that can lighten the appearance of skin or otherwise controllably affect skin pigmentation. For example, it may be desirable to lighten the overall complexion or color of a region of skin to alter the general appearance for cosmetic reasons. Also, lightening of particular hyperpigmented regions of skin, such as large freckles, ‘café au lait’ spots, melasma, or dark circles under the eyes that may result from excessive local amounts of pigment in the skin, may also be desirable for cosmetic reasons. Hyperpigmentation can result from a variety of factors such as UV exposure, aging, stress, trauma, inflammation, etc. Such factors can lead to an excess production of melanin, or melanogenesis, in the skin by melanocytes, which can lead to formation of hyperpigmented areas. Such hyperpigmented areas are typically associated with excess melanin within the epidermis; however, they can also result from excess melanin deposited within the dermis.
Hypopigmentation of skin tissue has been observed as a side effect in response to temporary cooling or freezing of the tissue, such as may occur during cryosurgery procedures. Loss of pigmentation following skin cooling or freezing may result from decreased melanin production, decreased melanosome production, destruction of melanocytes, or inhibited transfer of melanosome into the keratinocytes in the lower region of the epidermal layer. The resultant hypopigmentation may be long-lasting or permanent. However, it has also been observed that some of these freezing procedures can generate regions of hyperpigmentation of skin tissue. The level of increase or decrease in pigmentation may be dependent upon certain aspects of the cooling or freezing conditions, including the temperature of the cooling treatment, and the length of time the tissue is exposed to freezing conditions.
While some hypopigmentation treatments, devices, and systems have been previously developed, further improvements may be desired. Toward this end, it may be desirable to improve the consistency of skin freezing and the consistency of a duration of skin freezing. Such improvements may be desirable to improve overall hypopigmentation consistency. For example, with some cooling treatments, the skin may sometimes freeze toward the beginning of the cooling treatment, or may sometimes cool to a temperature below the freezing point (e.g., 0 to −5° C.) for a period and then freeze thereafter. With some cooling treatments, the skin may become supercooled (cooled to a temperature below the freezing point) and may not freeze at all during the cooling treatment. Such variability in the skin freezing (i.e., the formation of water ice in the skin) may result in less than optimal treatment.
In light of the above, it may be desirable to improve the consistency or repeatability of hypopigmentation treatments, in particular hypopigmentation treatments provided via skin freezing. At least some embodiments of the present invention may provide additional control over the occurrence of freezing and may limit supercooling or otherwise promote freezing of the skin during a cooling treatment.